[Equest-users] White Box Technologies brings simulation weather data to the satellite age
Joe Huang
yjhuang at whiteboxtechnologies.com
Tue Jan 2 19:15:27 PST 2018
Nick,
This is an interesting topic that has evolved in an unexpected way. Now that NREL has
mastered the technology of satellite-derived solar radiation, they have regarded weather
station data as an impediment, since there's no way to get such measured data to match the
5-kilometer grid of the satellite-derived solar. Therefore, they have abandoned the
weather station data (which was was used in all the TMYs to date) and gone instead to
Reanalysis Data from NOAA's MERRA, which is running a climate forecasting model in
retrospective mode. I don't have time now to discuss reanalysis, except to say that from
what I've seen the results are decidedly "iffy". Almost two years ago, I managed to get a
Work Statement through ASHRAE for someone to take a good look at reanalysis data.
So, what does this mean for your question? NREL's National Solar Radiation Data Base
(NSRDB) can now get you the hourly time series or a TMY for more than a million grid
points over the US, all with satellite-derived solar radiation but MERRA results for the
other climate parameters. I've told NREL several years ago that for the building
simulation industry it would be much better to merge the satellite-derived solar with
actual station data that give good accurate coverage of urban areas where buildings are
located. NREL's response was that they'd be happy to do this, but someone has to pay them
for the work.
In response to your hypothesis below, I think you're being too disparaging of the previous
modeling efforts while raising too high your expectations of satellite solar. It's not
that the previous models failed to account for local climate conditions, but that they
lacked good data to drive them. For example, all models included terms for cloud cover
and clearness, or for the more detailed physical models arcane parameters like aerosol
optical depth, preciptable moisture, etc., but how available are the input data and how
reliable are they? The advantages of satellite-derived solar are that they provide a
comprehensive and objective view of the cloud conditions, which combined with satellite
measurements of the atmospheric conditions and improved modeling, results in accuracies
that previous modeling efforts can not attain. As far as discerning localized effects of
smog and dust in urban areas, that would still depend on whether there's sufficient
monitoring at that spatial and time scale to detect the differences. What I mean is that
it's one thing to observe that in general urban locations have more smog and particulates
than rural locations, but it's something else to quantify the resultant differences in
solar radiation over time and distance.
I'd like to take the opportunity here to step back and comment on the status of weather
data for the building energy community, My interactions with NREL has brought the
realization that we have been piggy-backing on the efforts of others outside our community
for our weather data. I don't intend to pick on the NREL Solar Program, several of whom I
consider friends and colleagues, but their target client is the solar power industry.
Since solar power arrays can be installed anywhere, preferably in rural uninhabited
locations, it makes sense to go to satellite-derived solar. It's also clear that to serve
that industry, NREL would focus its efforts on getting the best solar values, while all
the other climatic parameters, like temperature, humidity, wind speed, etc., are
secondary, which may be why getting them from MERRA is a satisfactory choice. The focus
on solar is also evident in the weighting used by NREL to develop the TMYs, with 50%
weight placed on the 2 solar and 50% on the remaining 8 non-solar parameters.
For the building energy community, or priorities are somewhat different. Since 99% of
buildings are located in urban locations, we should focus much more on climate in urban
areas. Luckily, that's also where the great majority of existing weather are located,
which is why I'm resistant to throwing out measured weather data and replacing them with
synthetic data, no matter how much they've been "seeded" with real data. As for the
weighting of climate parameters in selecting the typical months, why not use building
energy simulations and weight them by the distribution of heating and cooling loads?
Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
On 1/2/2018 9:30 AM, Nicholas Caton wrote:
>
> Hi Joe,
>
> From your perspective, are NREL or any other government/professional bodies making
> moves/indications to update/refresh the current TMY3 sets to utilize satellite-derived
> solar radiation? Seems like a no-brainer for our industry, but is there a
> counter-argument? It seems likely, but has there been rigorous comparisons of
> satellite-derived solar radiation against measured values and/or our “present-day” solar
> models used to derive solar radiation information for building energy simulation?
>
> Also, I’m trying to understand and correctly characterize the impact of this development
> in simple terms my brain can follow. Is it fair to say:
>
> The solar models used in developing weather files for building energy simulations
> to-date in our industry (including all/most industry-standard TMY weather sets), because
> they have been using solar radiation derived from (evolving) solar models, have _not_
> accounted for the likes of local climate cloud cover / smog / dust? Seattle (~47°N) has
> perhaps been seeing as much sunlight through the winter as Paris (~48°N)?
>
> Does satellite-derived solar radiation address some or all of these local climate issues
> (cloud cover, smog, dust) affecting direct/indirect solar radiation?
>
> Thanks sincerely for all your teaching Joe,
>
> ~Nick
>
> *Nick Caton, P.E., BEMP*
>
> Senior Energy Engineer
> Regional Energy Engineering Manager
>
> Energy and Sustainability Services
> Schneider Electric
>
>
>
> D 913.564.6361
> M 785.410.3317
> F 913.564.6380
> E nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com>
>
>
>
> 15200 Santa Fe Trail Drive
> Suite 204
> Lenexa, KS 66219
> United States
>
> *From:*Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of
> *Joe Huang via Equest-users
> *Sent:* Thursday, December 14, 2017 8:13 PM
> *To:* BLDG-SIM <bldg-sim at lists.onebuilding.org>; EnergyPlus_Support
> <EnergyPlus_Support at yahoogroups.com>; equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] White Box Technologies brings simulation weather data to the
> satellite age
>
> It is with joy and some trepidation to report that White Box Technologies (WBT) is
> updating all its historical weather files with satellite-derived solar radiation. Joy
> because this overcomes what has been the most significant question mark with weather
> files; trepidation because of the amount of work needed to carry out and maintain this
> effort. To show that this is more than marketing hype, I need to give a rather long
> explanation about this development.
>
> The bane of weather data over the past three decades has been the solar radiation
> (global horizontal and direct normal) which are not measured parameters, but derived
> using various solar and sky models. All the familiar "typical year" sets, i.e., TMY,
> WYEC, IWEC, etc., let alone the historical weather files, have modeled solar radiation.
> Although a lot of
> work has gone into such models (see M. Iqbal,"An Introduction to Solar Radiation",
> Academic Press, 1983), there remain an almost intractible problem of the lack of good
> measured solar to tune any of these models. For example, in the ASHRAE IWEC2 weather
> files, my team was able to find one or two years' measured data for less than 50 locations,
> from which were derived 28 sets of regression coefficients then used for all 3,012 IWEC2
> locations.
>
> For the past decade and a half, researchers around the world have been working to derive
> solar radiation from weather satellite imagery, driven largely by the needs of the solar
> power industry for the siting of solar power plants and getting "bankable" solar
> estimates for their arrays. Our little building energy simulation sector can of course
> benefit by hanging on the coattails of the solar power industry, but the downside has
> been to be totally priced out, since the commercial cost for one year's solar data for
> one location (grid cell) typically runs around $1,000.
>
> A welcome development over the last five years is that various government offices or
> affiliated consortia are now beginning to also providing access to satellite-derived
> solar radiation at minimal or more acceptable costs under various conditions. Over the
> past three years, WBT has obtained access to such data and permission for its use in WBT
> weather files.
> WBT is now either replacing the solar radiation on its historical weather files, or
> using satellite-derived radiation to develop custom solar coefficients for each location
> to extend the satellite-derived solar to time periods outside the available time window.
> With the exception of polar locations above or below 60/66 degrees, island nations in
> the Pacific and Indian Ocean, and a few unfortunate "blind spots", the entire land mass
> is being covered with at least 10 years up to 18 years of hourly solar records.
>
> Starting in 2018, WBT historical weather files in the following areas will all have
> satellite-derived solar radiation for the following time periods: Europe, Africa, South
> America east of 66 West, i.e., Brazil and Uruguay (2004 to date), Australia (1999 to
> date), and East Asia (2007 to date, access pending). WBT historical weather files in the
> following areas will have satellite-derived solar radiation for the indicated time
> periods - North America and Central/South American down to 20 South (1998-2015), South
> Asia (2000-2014), with modeled solar radiation from 2016 on that has been individually
> tuned to the past satellite-derived solar.
>
> Another benefit to the satellite-derived solar is to increases the number of available
> weather stations, which in many places has been limited by the lack of cloud cover data
> needed to model the solar radiation. For reasons that are not immediately identifiable,
> several English-speaking Commonwealth countries has seen a marked drop in the number of
> available stations due to the decreases in the reporting of cloud cover (see plot, ZAF =
> South Africa). For example, the number of stations in the UK has dropped by almost 2/3s
> between 2001 and 2017 (174 to 64), but with satellite-derived solar, it will go back up
> to over 180, while in Australia and South Africa the comparable numbers are from 175 to
> well over 500, and from 37 to over 100, respectively.
>
> If interested, customers who have purchased a historical weather files from WBT over the
> past five years can get an updated weather file at no cost. Lastly, although it will
> take at least a month to update all 10,000 2017 files, it's very quick to do for any
> specific location or even 50 or so locations. Therefore, if you have an urgent request
> please e-mail me and I will put that at the beginning of the queue for that day.
>
> --
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 205A
> Moraga CA 94556
> yjhuang at whiteboxtechnologies.com <mailto:yjhuang at whiteboxtechnologies.com>
> http://weather.whiteboxtechnologies.com for simulation-ready weather data
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
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